duplicates:

• SR-1687 Swift does not warn about shadowing

relates to:

• SR-8524 Shadowing in protocols leads to difficult to find bugs

Issue Description:

The problem is illustrated at http://stackoverflow.com/questions/39983561/swift-3-silently-allows-shadowing-a-parameter

This really, really leads to hard-to-spot bugs. Please reconsider, and add an appropriate warning to the compiler.

Sample code:

func f(_ x: inout Int?) {
var x: Int? // <– this declaration should produce a warning
x = 105
if x! < 1000 {}
}

var a: Int? = 3
f(&a)
print("(a)")